This invention relates to enamine derivatives, precursors thereof, processes for producing the same and an electrophotographic member containing such enamine derivatives.
There have been known enamine derivatives having various substituents [e.g. J. Imaging Science 29, pp. 7-10 (1985), Japanese Patent Unexamined Publication Nos. 62-237458, 62-244061, etc.]. These compounds are used as a charge transport material mainly in a charge transport layer of electrophotographic member for copying machines and laser beam printers. The charge transport layer is generally formed by coating a coating solution for charge transport layer prepared by mixing a charge transport material, a binder and a solvent for dissolution on a substrate using an applicator. In order to obtain a practically usable film thickness of 15 .mu.m to 25 .mu.m of the charge transport layer, it is generally necessary to make the total solid content (a total of a charge transport material and a binder) in the coating solution for charge transport layer about 15 to 20% by weight. Further, in order to obtain excellent electrophotographic properties, it is effective to enhance the mixing ratio of the charge transport material to the binder.
But known enamine derivatives have problems in solubility in solvents and/or compatibility with binders. For example, 1,1-bis(p-ethoxyphenyl)-2-[N,N-bis-(4-methoxyphenyl)amine] is relatively excellent in solubility in solvents compared with known enamine derivatives. When this compound is mixed with a binder of bisphenol A type polycarbonate (Lexan 141, a trade name, mfd by General Electric Company) in an amount of 35% by weight per total solid content to prepare a coating solution for charge transport layer and to form a charge transport layer, the resulting charge transport layer seems to have good compatibility of the enamine compound with the polycarbonate resin in appearance. But when this layer is peeled off and subjected to differential scanning calorimetry, the glass transition point of the layer and that of the binder appear separately as shown in FIG. 15. This means that the polycarbonate resin and the enamine compound are phase separated microscopically and not compatible in the layer. An electrophotographic member containing such a charge transport layer which is phase separated microscopically has defects in that electrophotographic properties are lowered, particularly residual potential is undesirably raised.